Conventional fingerprint sensing devices may be classified into two major types, including optical fingerprint sensing devices and capacitive fingerprint sensing devices. The optical sensing devices may include a light source, a prism and an image-sensing element (e.g., a camera). When a user's fingertip is placed on the prism, the image-sensing element is able to capture the fingerprint image by taking into account the varying luminous intensity of light reflected from the ridges and valleys of the fingertip. However, inclusion of the prism causes conventional optical fingerprint sensing devices to be relatively bulky in size and have limited applicability in handheld electronic devices. In the case of conventional capacitive fingerprint sensing devices, generation of the user's fingerprint image usually involves the inclusion of high-density capacitive or pressure sensors that detect charge variations between ridges and valleys of the fingertip. Although the conventional capacitive fingerprint sensing devices are relatively compact in size, the production cost is relatively high and the image resolution is relatively low.
Referring to FIG. 1, U.S. Pat. No. 8,569,875 discloses a fingerprint sensing device 1, comprising a chip 11, a circuit substrate 13, and a package 14. The chip 11 is disposed on the circuit substrate 13 and has a top surface 111 including a sensing region 112, and a plurality of connecting pads 113 that are electrically coupled to the conductive pads 131 of the circuit substrate 13 via metal wires 12 for signal transmission. The package 14 partially encapsulates the chip 11 to expose the sensing region 112 for contact with a user's fingertip, as well as to protect the electrical connection between the connecting pads 113, the conductive pads 131 and the connecting wires 12. However, such configuration of the package 14 requires special molds to prevent a molding material from coming into contact with the sensing region 112 during the formation of the package 14. In addition, since the package 14 is not coplanar with the sensing region 112 of the chip 11, finger movement of the user may be limited.